Mycotoxins

Mycotoxins are chemicals that are produced by filamentous fungi that affect human or animal health. By convention, this excludes mushroom poisons. These fungi are called toxigenic fungi. All of these species are deuteromy-cetes (asexual) some of which have a known ascomycetous (sexual) stage. All of the mycotoxins discussed here are secondary metabolites of the fungi concerned, that is, compounds that are produced after one or more nutrients become limiting (1-3). The occurrence of mycotoxins is entirely governed by the existence of conditions that favor the growth of the fungi concerned. Under environmental conditions, different fungal species are favored as diseases of crop plants or as saprophytes on stored crops and sometimes other materials. When the conditions favor the growth of toxigenic species, it is an invariable and unfortunate rule that one or more of the compounds for which the fungus has the genetic potential are produced. Modern methods of agriculture appear to be selecting for increased prevalence of toxigenic strains (4).

With modern studies of toxigenic fungi, it has been appreciated that they can produce many compounds, often from different biosynthetic families. The ecological significance of the occurrence of these mixtures has been a fertile area of study in recent years. As it relates to human and animal toxicology, the potency of the contaminated material is due to the mixtures present (5,6). At the time of the discovery of penicillin and the first wave of fungal-derived antibiotics, the researchers believed that these compounds were active in nature. In the postwar period, secondary metabolites were characterized as everything from waste products to the consequences of "displacement activities" of the fungi. The current view is that these compounds are important as virulence factors and as mediators of interference competition; that is, they exclude competing microbes and animals from the food source (4,7,8).

Mycotoxins have affected human populations since the beginning of organized crop production. Ergotism is discussed in the Old Testament of the Bible. Some claim that the ancient Chinese used ergot for obstetrical purposes 5000 years ago. Many epidemics of ergotism were reported in western Europe from about a.d. 800. The screams of the

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Lauren Jackson FDA-NCFST Argo, Illinois

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